It is particularly important to wheelchair users who have physical disabilities and associated posture and postural control impairments, such as those typically caused by congenital disorders, to achieve an optimal seating and support position on the wheelchair. It is equally important to do the same for wheelchair users who have a more typical size and shape but have been disabled by acquired or traumatic injuries or debilitating disease. These individuals spend most of their waking hours residing in a wheelchair. Obtaining individualized support and alignment of the wheelchair user is important for optimal mobility, function, health and safety. Without achieving the proper and safe posture, the wheelchair user may be susceptible to further deterioration in physical capabilities, due to progression of postural deformity and associated deterioration of health and mobility as well as increased risk for pressure ulcers induced from sitting.
To achieve the correct postural alignment of the user in the wheelchair, it is necessary to locate and support the seat cushion and the back cushion in an individualized manner according to the posture and physiology of the wheelchair user. In the case of the seat cushion, much of the support arises from the contour of the cushion. Positioning the back cushion is usually considerably more complex, because more adjustments are required. The back and upper torso of the wheelchair user must usually be positioned relative to the seat cushion, to achieve balance on the wheelchair so the user does not experience a tendency to fall or lean forward, backward or sideways. In some circumstances, the physiology of the back and upper torso of the wheelchair user is complex in shape, requiring more support than with a more typical physiology.
These complexities in back support have led to the recognition that a maximum amount of adjustment capability is desirable. In general, that maximum amount of adjustment requires adjustments along and about the three mutually perpendicular longitudinal, transverse and vertical axes. The capability to make adjustments in each of these six realms of possible movement (longitudinal and pivotal moment along and about the three mutually perpendicular axes), assures maximum flexibility in achieving the optimum position for support and the most healthy outcome.
A number of back support devices have been developed which provide longitudinal and pivotal movement in one or all of the three mutually perpendicular axes. Those back support devices which provide longitudinal and pivotal movement in all three mutually perpendicular axes are usually the most desirable for use. However, the prior three-axis longitudinal and pivotal movement back support devices are very complex in construction, with many moving parts having complex interdependent relationships and positions, which a physical therapist or wheelchair seating professional may not fully appreciate or fully utilize when fitting the back support device to the wheelchair user. Furthermore, adjustments can be achieved only with great difficulty and effort, due to the mechanical complexity of the device. In many cases, the positioning on or about one axis is so interdependent with the positioning on or about one or both of the other two axes that an adjustment along or about one axis creates the undesirable effect of changing the position on or about one or more of the other two axes, making it extremely difficult and time-consuming for the fitting therapist or seating professional to achieve optimal support and positioning. The complexity of the device complicates the effort, since many physical therapists and wheelchair seating professionals have difficulty understanding the mechanical relationships involved in adjusting the numerous elements. Adjustments are also complicated by the necessity to insert separate shims and adjustment elements into the mechanical structure, and the necessity to disassemble parts to make adjustments. Losing or misplacing parts is constant risk, and the back support device cannot be used until replacement parts are obtained.
The complexity of prior mechanical back support devices also frequently leads to loss of the optimal position, because the nature of the mechanical devices make them susceptible to slip from the initial adjusted position. The mechanical features of prior back support devices also cause them to feel or to be perceived as loose in assembly or connection to the wheelchair. Such a feeling is extremely disconcerting to the security of a wheelchair user, since the user usually depends on the mechanical integrity of the support device when controlling the wheelchair and to prevent falls from the wheelchair. Many prior back support devices are also heavy, which adds to the effort of maneuvering the wheelchair. Many prior back support devices are not aesthetically pleasing in appearance, which also detracts from the persona or self-image of the wheelchair user.